Oh that is scary news to hear and consulting an oncologist is a good idea.

Pyogranulomatous is an inflammatory process which is often the formation of nodules in fatty tissues.

Necrotizing steatitis means the tissue cells are destroying themselves or dying from the inflammatory process.

Peripheral means edge.

Fibrosis is the excess production of connective tissue (fibers) as a healing attempt (scar tissue for example).

You can read about one issue called yellow fat disease here

http://www.cat-world.com.au/steatitis-yellow-fat-disease-in-cats

http://www.vetmanual.org/mvm/index.jsp?cfile=htm/bc/91402.htm

and another problem panniculitis here

http://www.gopetsamerica.com/dog-health/panniculitis.aspx

Your best bet is that second look by an oncologist to determine the treatment steps to take.

Hope this helps you!

The articles I included in the above answer mentioned possible causes and there may be more.

One issue might be diet including a diet high in tuna.

An immune disease is a possibility as is vaccination injection reaction or a foriegn body under the skin. Could be this was all triggered by infection under the skin from a cat bite or claw.

This is why seeing a specialist is a good idea. Find out the underlying possible issues and see what applies to your pet's situation.

Part of having multiple pets is you end up seeing more health issues than the person who has only one or two pets.

You can read here some more causes

http://tinyurl.com/yka2ck3

and FIP may be implicated too.

I can't make you be happy with what I've told you but there is a limit in what can be done over the net. You need in person veterinary exam and consultation to have a good idea what is going on with your cat and perhaps finding a 'why' for it or perhaps not.

You might never know if during play one cat slightly punctured the skin of another one and that is simply one possible option not the only option.

You need to pursue this with in person vet care.

You are very welcome - I hope your vet can him feeling better for you.

I do have great sympathy for your situation. I just went back and added it up to realize I've lost 9 pets in the last 2 years - all seniors of varying ages. Its just not easy.

I don't know if you have seen www.petloss.com or the rainbow bridge story you may find some comfort there with your losses in the past.

Thanks for the above accept.

I like the rainbow bridge concept but I can't read it either.

I can tell you that remembering all the funny happy things do push the sadness away for me.

Siamese are special any how - our old boy is 19 1/2 and not doing so well but still full of 'comments' about the world.

I'll close this down and I'm thinking positive thoughts for the current cat for you!

Thanks for the kind comments.

I do think without the animals our lives would be less rich despite our wallets never being full because we have them!

So true!